How troubling is ocean acidification?

Not every commercial fisherman is convinced that curbing carbon
emissions is necessary to stop global warming. But the evidence that
fossil fuel pollution is making the oceans more corrosive—and removing
building basic building blocks of the marine world—starts to get their
attention.

If you sliced open the bellies of our most popular eating fish, at
one point in their life cycle you would probably find krill, plankton,
oceanic snails or other shelled creatures—the kinds of species likely to
run into trouble as the oceans absorb more carbon dioxide from burning
fossil fuels and other industrial processes.

As those carbon emissions rise, seawater becomes more acidic and sea
life has more trouble finding calcium carbonate, a basic building block
that many creatures need to build shells or skeletons, and, ultimately,
to survive.

I guess you could call it a second-order threat, but it’s
still pretty immediate. I think this really is probably the most
fundamental challenge we’ve got. There’s all this handwringing about the
health of the oceans and people say ‘well, we’ve just got to manage
fisheries better and maybe create some marine protected areas and
everything will be fine in the garden.’ And that’s really not (the
case). …We’ve really got to figure out how to burn a lot less fossil
fuel and shift away from carbon-based policies.

Some might argue that oceans are resilient places, that nature abhors
a vacuum, and that other kinds of algae or grasses that thrive in more
acidic seas could replace losses at the bottom of the food web. In
truth, we don’t yet know how complicated marine ecosystems will adapt to ocean acidification. The effects could range from minor to apocalyptic.

In that sense, you get to choose how scared you want to be, says Brad Warren, who directs the Sustainable Fisheries Partnership’s ocean acidification program.
But the most knowledgeable scientists tend to eschew the more
optimistic view, he said. And a smart businessperson pays attention to
signs of trouble, tries not to get caught behind the curve, and needs to
rethink old strategies when they’re no longer working. In other words,
says Warren:

If you think of someone who has a fiduciary duty for the
systems that feed us and provide jobs to half a billion people in the
world—from subsistence hunting to those making a lot of money—one can
view that with a gambler’s instinct or with a stewardship instinct. What
would you rather be—a banker or a gambler—with this resource?

‘Different might be OK – Maybe‘

An ocean rich in calcium carbonate is like a nutritious miso soup,
providing essential ingredients that everything from plankton, corals,
mussels, oysters, crabs, scallops, lobsters, sea urchins and abalone
need at some stage in their life cycle. As waters become more acidic,
and calcium carbonate becomes less available, some of these species have
trouble building shells, don’t grow as fast, or become stunted. As pH
drops even lower, those protective coatings or internal structures can
begin to dissolve.

“The thing that people really don’t appreciate is how many organisms
have these calcium carbonate mineral phases,” said Burke Hales, an
Oregon State University oceanographer.

The chart below shows that about half the annual catch in the US
comes from mollusks and crustaceans, many of which use calcium
carbonate. Another 24 percent are the animals that directly feed upon
those “calcifiers.”

Laboratory studies conducted so far indicate that some of the direct and indirect effects of increasingly acidic oceans include:

Plankton: Some forms of plankton that other animals
rely on for food struggle or die under low pH conditions. Pteropods—tiny
winged sea snails comprise up to 60 percent of the diet of some
juvenile salmon—have dissolved in low pH water. Embryos of Antarctic krill—which makes up a huge percentage of the diet of the southern oceans—have failed to hatch in highly acidic waters.

Structure: Species that provide key underwater
habitat for other creatures are vulnerable to ocean acidification. Coral
reefs, which support a huge amount of biodiversity, are among the least tolerant of low pH waters. If oyster populations crash, eventually oyster beds that help support everything from sea anemones to sportfish will suffer.

Other chemical and nutrient changes: Ocean acidification may affect the availability of other nutrients and trace metals, altering the composition of microscopic plant communities that other creatures eat.

Uncertainties about how these changes will play out across an entire
ecosystem make it impossible to tally all the potential losses. One narrow case study found
that if oysters and mussels decline in the wild at the same rate that’s
been observed in the laboratory, we could expect $75 million to $187
million in annual losses in the US mollusk catch.

And, as the following chart shows, not all fisheries around the world will be affected equally.
Below, the red colors include mollusks most likely to be affected by
acidification, yellows indicate crustaceans, greens indicate predators
that may be indirectly affected by food web effects, and blues indicate
species whose responses to ocean acidification are unknown.

Sarah Cooley, a Woods Hole Oceanographic Institution researcher
working to put an economic value on ocean acidification’s potential
consequences, explains in a very readable interview with Oceanus Magazine that Alaska’s fisheries (which produce 60 percent of the seafood in the US
and where much of the Northwest fleet fishes) may be less vulnerable
than New England fisheries that rely much more heavily on mollusks.

But the Alaskan catch could also decline, she said, because fish like
haddock, halibut, herring, flounder, and cod eat mollusks themselves.
And that could potentially affect top predators like swordfish, tuna,
shark, and salmon.

Her research suggests that
the fishing industry itself—along with our eating habits—may be in for a
change. As oceans become more acidic, we may have to eat other species,
shift aquaculture production to creatures that are less vulnerable, or
move aquaculture operations to geographic areas that are less affected
(all of which are likely to raise costs.)

In sum, Cooley says:

The [natural] communities are going to be very, very different. And different might be OK—maybe.
There still is an ecosystem to be had. But a lot of the things that we
really enjoy, that our communities depend on, are not going to be there.
We may be able to find other awesome things about the new communities,
but chances are, the options will be limited.

New Carbon Policies Required

While it’s prudent for people to be concerned about ocean
acidification, it’s not sufficient, said Warren, of the Sustainable
Fisheries Partnership. While it may take decades to moderate the effects
of carbon dioxide that the oceans are absorbing today, there are things
that can be done now to improve the situation: develop extensive
monitoring networks, invest in ocean acidification research, get a handle on stormwater and other sources of pollution that flush nutrients into our waterways.

While the seafood industry is by no means monolithic, Warren said, it
trends conservative politically. But the threats from ocean
acidification are causing some in the industry to advocate for the only
direct solution: reducing carbon dioxide emissions.

We work with people who cover the full range of opinions
on that stuff. There are some people who think that Al Gore and the
Tooth Fairy come from the same planet, but when they get their heads
around this problem, some of those guys really go through a rethink.

You can use taxes, carbon markets, you can implement
other controls, energy efficiency, increased use of cleaner power. There
are many tools, but no one I think can credibly argue that you can do
it without some kind of carbon policy. However you design it, or
whatever axiom of change you bring to it, you’ve got to bring the actual
flow of emissions under management.

In our next post, we’ll take a closer look at existing laws that
could be used to address ocean acidification and what kinds of new
policies will become necessary.

Essays in the Range blog are not written by High Country News. The authors are solely responsible for the content.